INDICATION OF SOIL POLLUTION BY MICROBIOLOGICAL AND BIOCHEMICAL METHODS

Microbiological and biochemical methods (Novak, 1960, 1963; Filip et a i., 1994) have been used to identify the ecotoxicologically relevant s oil loads by hazardous elements. We used the simulated contamination ( Cd 10 and 3, Cu 150, Ni 150, Zn 400 mg . kg(-1) in form of sulphates) of samples from the Ap horizons of agriculturally used soils (arenic R egosol, glossalbic Luvisol, dystric Cambisol, cambic Podsol, histic Gl eysol, calcic and pelic Chemozem). Barley was grown on soils, contamin ation of which slightly surpassed the maximum permissible limits of tr ace hazardous elements (TEs). Soil units are in the first experiment c haracterized (Tab. I) by soil-specific and by liming affected (pH 6.5 to 6.8) differences in the amount of aerobic bacteria, actinomycetes a nd micromycetes, especially in the first rum of the experiment. Inhibi tion of aerobic bacteria by Zn manifests itself especially in Regosol and Luvisol, by Cd in Podsol. Actinomycetes show opposite responses du e to the competition. Micromycetes number was reduced only in Regosol by Zn. Chemozem was not affected. Biochemical tests (Tab. II) proved t hat soil-specific characteristics were more expressive than contaminat ion impacts. Inhibition of N mineralization, potential nitrification a nd N immobilization by Zn (Cu) was found in Regosol and Luvisol, by Cd in Podsol. High values of N immobilization by the end of the experime nt were caused by the gradual increase of synthetic activities of micr oorganisms; in Chernozem they reflect the soil-specific features. The mentioned results reflect soil vulnerability relationships among soils , testified (Podlesakova, Nemecek, 1991) by plant uptakes of TEs in th e sequence Regosol > Luvisol > Podsol > Chernozem for Zn (Ni, Cu), whi ch is shifting to the sequence with Podsols on the first place for Cd. They also correspond to phytotoxicity responses. In the next experime nt the comparison between limed and nonlimed variants expressed (Tab. III) the strong influence of the pH regulation on the raise of bacteri a and actinomycetes amount in all soils with a low buffering capacitie s and increase of Azotobacter. Inhibition of bacteria and actinomycete s by Zn was observed in most soils (except of Chernozems) before the p H regulation, after liming only in Regosol and Luvisol, inhibition of Azotobacter in Regosol. Micromycetes were affected by Zn (Ni) in nonli med Regosol, by Cd (Ni) in Podsol. Tab. IV presents the use of a new s et of methods (Filip et al., 1994) for identification of Zn impacts. T he most conspicuous feature of these results is the stimulating influe nce of Zn in the last turn of experiments on bacteria, including the o ligotrophic ones in Podsol and Chernozem. This effect is accompanied b y an increased N mineralization, followed in Chernozem by nitrificatio n and by decrease of dehydrogenase activities. No inhibition was ident ified in Regosol and Luvisol. When we compare the obtained results wit h TEs mobilities and plant uptakes (Podlesakova, Nemecek, 1996) we arr ive at the statement that microbiological and biochemical tests cannot replace methods destinated for the direct indication of hazards for d efined transfer pathways. But they are able to confirm findings of dir ect prediction methods. We are also aware of the fact that data from a rtificially contaminated soils have to be interpreted in terms of soil vulnerability. The research with soils polluted in the field continue s.